1. letter bomb - Noun
2. letter bomb - Verb
a thin explosive device inside an envelope or package and detonated when opened
send an explosive to
Source: WordNetThe Unabomber letter bombed a number of individuals and institutions Source: Internet
In 1980 another letter bomb cost him the fingers of his left hand. Source: Internet
The letter bomb may have been in use for nearly as long as the common postal service has been in existence, as far back as 1764 (see Examples). Source: Internet